1. Field of the Invention
This invention relates to an image-tremble-correcting system for an optical instrument having an image-focussing lens system, such as a still camera, a video camera, a telescope, a pair of binoculars or the like, to correct a tremble of a focussed image caused by an oscillation of the optical instrument due to, for example, a hand tremble.
2. Description of the Related Art
For example, such an image-tremble-correcting system is frequently incorporated in a photographing lens system of a single lens reflex (SLR) type camera. The image-tremble-correcting system comprises a movable image-tremble-correcting lens system assembled in the photographing lens system, a tremble sensor system that detects an amount of tremble of the camera, and therefore a focussed image, caused by an oscillation of the camera due to, for example, a hand tremble, and a driving system that moves the movable image-tremble-correcting lens system to thereby neutralize the tremble of the focussed image.
Of course, the movement of the image-tremble-correcting-lens system is mechanically limited, and thus it is impossible to correct the tremble of the focussed image beyond the limits of movement of the image-tremble-correcting-lens system. Although it is possible to widen the range through which the image-tremble-correcting-lens system can be moved, widening of the range is impossible without an increase in bulkiness of the photographing lens system.
As is well known, in the SLR camera, an image to be photographed is observed via a viewfinder system through the photographing lens system, and the image-tremble-correcting system is operated when a release switch button is partly depressed, i.e. when a photometry switch is turned ON to perform a photometry measurement. Thus, while the image to be photographed is being observed through the viewfinder in the course of the photometry measurement, image tremble is corrected.
During the photometry measurement, the SLR camera is often panned widely in vertical and/or horizontal directions to frame the image to be performed. At this time, the image-tremble-correcting-lens system may easily reach a limit position due to the wide movement of the SLR camera in the vertical and/or horizontal directions, resulting in an awkward motion of the image as observed through the viewfinder system. Of course, the awkward motion of the image gives a photographer an uncomfortable feeling.
Note, the same is true for other optical instruments, such as a video camera, a telescope, a pair of binoculars or the like.
Therefore, an object of the present invention is to provide an image-tremble-correcting system for an optical instrument, which is constituted such that vertical and horizontal limitations of movement of an image-tremble-correcting-lens system can be widened without increasing the mechanical bulkiness of a photographing lens system.
In accordance with the present invention, there is provided an image-tremble-correcting system for an optical instrument, having an optical focussing system for producing a focussed image, to correct a tremble of the focussed image caused by an oscillation of the optical instrument. The image-tremble-correcting system comprises a movable optical tremble-correction system assembled in the optical focussing system of the optical instrument, and an X-Y rectangular coordinate system which is defined on a geometrical plane perpendicular to an optical axis of the optical focussing system. An origin of the X-Y rectangular coordinate system coincides with the optical axis of the optical focussing system, and the X- and Y-axes thereof define an angle of 45xc2x0 with a horizontal axis and a vertical axis defined on the geometrical plane when the optical instrument is positioned at a usual attitude. The image-tremble-correcting system further comprises a first position-detecting system that detects a position of the movable optical tremble-correction system along the X-axis of the X-Y rectangular coordinate system, a second position-detecting system that detects a position of the movable optical tremble-correction system along the Y-axis of the X-Y rectangular coordinate system, a first driving system that moves the movable optical tremble-correction system along the X-axis of the X-Y rectangular coordinate system, a second driving system that moves the movable optical tremble-correction system along the Y-axis of the X-Y rectangular coordinate system, a tremble-sensor system that detects an amount of tremble of the focussed image with respect to the X-Y rectangular coordinate system, and a controller that controls the first and second driving system to move the movable optical tremble-correction system along the X- and Y-axes of the X-Y rectangular coordinate system, such that the amount of tremble of the focussed image is neutralized.
Preferably, the movable optical tremble-correction system is movable along the X-axis and the Y-axis of the X-Y rectangular coordinate system to the same extent, such that the movement of the movable optical tremble-correction system is restricted in a square area.
The image-tremble-correcting system may further comprise a first limit-position-determination system that determines whether the position detected by the first position-detecting system is a first limit position along the X-axis of the X-Y rectangular coordinate system, a first correction-limit-determination system that determines whether an amount of tremble of the focussed image along the X-axis of the X-Y rectangular coordinate system exceeds the first limit position, when it is determined by the first limit-position-determination system that the position detected by the first position-detecting system is the first limit position along the X-axis of the X-Y rectangular coordinate system, a second limit-position-determination system that determines whether the position detected by the second position-detecting system is a second limit position along the Y-axis of the X-Y rectangular coordinate system, and a second correction-limit-determination system that determines whether an amount of tremble of the focussed image along the Y-axis of the X-Y rectangular coordinate system exceeds the second limit position, when it is determined by the second limit-position-determination system that the position detected by the second position-detecting system is the second limit position along the Y-axis of the X-Y rectangular coordinate system.
In this case, the controller ceases controlling the first driving system when it is determined by the first correction-limit-determination system that the amount of tremble of the focussed image along the X-axis of the X-Y rectangular coordinate system exceeds the first limit position. Similarly, the controller ceases controlling the second driving system when it is determined by the second correction-limit-determination system that the amount of tremble of the focussed image along the Y-axis of the X-Y rectangular coordinate system exceeds the second limit position.
The tremble-sensor system may include a first angular speed sensor that detects a first angular speed of the optical instrument around the X-axis of the X-Y rectangular coordinate system, and a second angular speed sensor that detects a second angular speed of the optical instrument around the Y-axis of the X-Y rectangular coordinate system. In this case, the controlling of the respective first and second driving systems by the controller is performed on the basis of the first and second angular speed detected by the first and second angular speed sensors.
Preferably, the respective first and second driving systems comprise a first electromagnetic driving system and a second electromagnetic driving system. In this case, both a direction and a magnitude of an electric current, flowing through the first electromagnetic driving system, is controlled by the controller on the basis of the position of the movable optical tremble-correction system, detected by the first position-detecting system, and the first angular speed detected by the first angular speed sensor, thereby determining both a direction and an acceleration of the movement of the movable optical tremble-correction system along the X-axis of the X-Y rectangular coordinate system. Similarly, both a direction and a magnitude of an electric current, flowing through the second electromagnetic driving system, is controlled by the controller on the basis of the position of the movable optical tremble-correction system, detected by the second position-detecting system, and the second angular speed detected by the second angular speed sensor, thereby determining both a direction and an acceleration of the movement of the movable optical tremble-correction system along the Y-axis of the X-Y rectangular coordinate system.
For example, the optical instrument may comprise a single lens reflex camera having a photographing optical system as the optical focussing system. In this case, preferably, the movable optical tremble-correction system, the first and second position-detecting systems, and the first and second driving systems are assembled as an image-tremble-correcting unit in the photographing optical system.